Candidates for president are known for holding their tongue in public but cussing up a storm in private, witness confrontations involving John McCain and wife, Cindy, and Hillary Clinton and advisers, recounted in the bestselling book “Game Change” on the 2008 presidential election. Even Barack Obama briefly lost his cool.

But nothing has even stopped billionaire real estate mogul Donald Trump from public vulgarity. While contemplating a run for the White House in 2012, he talked to a Nevada Republican women’s luncheon about oil imports from the Middle East, saying: “We have nobody in Washington that sits back and said, ‘You’re not going to raise that f*****g price.’ ‘

Trump was set off Wednesday in Florida by a malfunctioning microphone, not unusual on the road to the presidency. (“If we can send a man to the moon, we can develop working public address systems,” the late Sen. Eugene McCarthy once quipped.) The result was a rant.

“And by the way, I don’t like this mic,” said Trump. “Whoever the hell brought this mic system, don’t pay the son-of-a-bitch who put it in. No, this mic is terrible, stupid mic keeps popping. Do you hear that, George. Don’t pay him. Don’t pay him!

“You know, I believe in paying but when somebody does a bad job, like this stupid mic, you shouldn’t pay the bastard. Terrible! Terrible!”

Trump was violating another rule of the campaign trail. Don’t publicly ridicule the help. A long ago 1948 incident helped President Harry Truman score the greatest come-from-behind win in American history.

A railroad engineer accidentally caused Republican candidate Thomas E. Dewey’s campaign trail to lurch back toward a campaign crowd. An angry Dewey snapped: “That’s the first lunatic I’ve had for an engineer. He probably should be shot at sunrise, but we’ll let him off because nobody was hurt.”

The Dewey remark was mimeographed and distributed to railroad workers and other union members around the country.